1. Field of the Invention
This invention relates to an image processing method for a color scanner, and more specifically to an image processing method for a color scanner of a plane scanning type, which is adapted to prepare a color separation for printing C (cyan), M (magenta), Y (yellow) and K (black) as If-toned after color separating signals which are obtained by linearly scanning a color original have been color corrected, sharp intensified and gradation converted and so on, and in which highlight and shadow points of the color original required for the signal processing are selected out of a display picture frame of a color monitor for designation.
2. Description of the Prior Art
The prior art has heretofore proposed a layout retouch system which is so called the "total system" in a printing plate making process. This total system is adapted to input a pattern input by a digitizer to display patterns and images (pictures) in a color cathode ray tube (CRT). a color original is scanned by a color scanner at a specified magnification and is stored in a memory means after A/D conversion. A stored color original is displayed in the color CRT according to inputted pattern information and edited by an interactive input in a main memory of a computer, and is then restored in the format corresponding to the output picture frame in a memory. Next, the color image information according to the output picture frame after editing is D/A converted and inputted to an output control circuit for the color scanner, thereby obtaining a described layout image. Disadvantages derived from such a layout retouch system are in that a great capacity of a storage medium is required for storing the information of the color original, and that a high speed computer is needed for edition process, thus rendering the system arrangement highly expensive and taking much time for edition process and the like.
A proposal (Japanese Patent Laid-open No. 59-11062) has made to provide an image input and output system by which the aforementioned shortcomings are eliminated, as shown in FIG. 1. A color original 2 pasted on a rotatable input drum 1 is image outputted in a dot form to a color paper 11 pasted on a rotatable output drum 10 according to information as pattern inputted by a digitizer 14. The color original 2 is scanned in a dot form by a read head 21 and then is color separated. A color separated signal CS therefor is inputted to a logarithmic converting circuit 3 by which the color separated signal CS is converted to a density signal DN. The density signal DN is then converted in an A/D converter 4 to a digital density signal DS. The digital density signal DS is inputted to a signal processing section 5 and a microprocessor 12 and is subjected by the signal processing section 5 to processes color correction, sharpness intensification, gradation conversion and the like. An image information DSA as processed is converted to an analog signal by a D/A converter 6 and is then inputted to a modulator 8 in a laser beam printer to modulate a laser beam from a laser oscillator 7 thereby exposing in a dot form on the color paper 11 of the output drum 10 by an output head (not shown).
On the other hand, a console 16 is provided for a data and command input unit and is adapted to input the inputted data and the like to the computer 13 by which the processed information is displayed in a graphic display 15 of an interactive type. The computer 13 is also connected to the microprocessor 12 of a subsystem. The density signal DS from the A/D converter 4 is inputted to the microprocessor 12 which is further connected to the signal processing section 5 for computing process. It is noted that the positions of the input and output drums 1 and 10 are respectively detected by detectors (not shown). The position information thereof being inputted to an operation controller 9. At the same time, the operation controller 9 is connected to the microprocessor 12 so as to drive and control a positional relation between these input and output drums 1 and 10 relatively by means of the operation controller 9. The digitizer 14 includes the origin coordinates and X-Y axes inherent in the device and may move the origin to a desired point and readily rotate the coordinates by processing the signal. Locations where the images are placed on the digitizer 14 and the input drum 1 may establish a corresponding guide such as a pin or the like in a plurality of common positions. The digitizer 14 is in turn connected to the computer 13 to input a shape of the image and desired positional coordinates.
The aforementioned image input and output system, shown in FIG. 2, is designed so that the color original 2 is directly pasted on the transparent and smooth surfaced cylindrical input drum 1 formed of glass or the like when reading the original, and that a light source 20 inside the input drum 1 emits light to the color original 2 whereby a transmitted light LT from the color original 2 is received by the read head 21 to input the image of the color original 2. In the instance, if a clearance on the order of a wave length of light is provided between the color original 2 and the input drum 1, Newton's rings (interference fringe) are formed between the back of the color original 2 and the surface of the input drum 1 under the infringe action of light to present uneveness in density in a striped form on the color original 2 thereby deteriorating the quality of the color original. For this reason, conventionally hyperfine grain powder is scattered between the color original 2 and the input drum 1, or fillers are applied thereto. Disadvantages derived from the use of the powder or the fillers are in that the former renders grain visual at a higher magnification of the image and involves a difficulty in handling, and that the latter causes troubles in application, wiping and so on.
The conventional color scanner has required a skilled operator for determining the conditions of color separation and color processing. However, the time required for determing these conditions takes more than the period of time for which the scanner is actually operated. Particularly, the quality of finished image depends upon determination of highlight and shadow points of the image required for the signal processing so that the operator determines the above points with the most serious of attention. In addition, the conventional color scanner is complicated in its operation.